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Have you ever wondered where the most mold and germs are hiding in your house? In this hands-on mold experiment for kids, we tested different surfaces around our home to see where mold spores would grow the fastest. The results were honestly surprising… and a little gross!

This mold growth experiment is a fantastic way to explore:

• fungi and mold spores
• scientific observation
• the scientific method
• food decomposition
• moisture and bacteria
• variables in science experiments

Kids love this activity because it feels like real science investigation work. Parents and teachers love it because it combines biology, microbiology, and STEM learning in a memorable hands-on way.

Just be warned… after doing this experiment, everyone suddenly wants to wash their hands a LOT more often.

What Is Mold?

Mold is a type of fungus that grows on organic materials. Tiny mold spores float through the air all around us, but they are usually too small to see. When spores land on moist surfaces with nutrients available, they can begin growing quickly.

Mold belongs to the fungi kingdom and spreads using thread-like structures called hyphae. Groups of hyphae form a network called mycelium, which helps the fungus absorb nutrients from its food source.

Mold can grow:

• on food
• in damp bathrooms
• on wet carpet
• around air conditioners
• on bread
• on fruit
• inside refrigerators
• or anywhere moisture is present

Different types of mold thrive in different conditions, which makes mold experiments fascinating for kids to observe.

Mold Experiment for Kids

This simple mold experiment allows kids to test different surfaces and observe mold growth over time.

We used gelatin and swabbed household surfaces to see where the most mold spores were hiding. You could also do this experiment with slices of bread, apples, cheese, potatoes, or other foods.

Supplies You Will Need

• Unflavored gelatin
• 2 cups boiling water
• Sanitized jars, plastic cups, or petri dishes
• Cotton swabs or q-tips
• Permanent marker
• Labels or masking tape
• Gloves
• Aluminum foil or lids
• Sealed bags if using bread
• Notebook or printable observation sheets

How to Do the Mold Experiment

Step 1: Prepare the Gelatin

Boil 2 cups of water and prepare the gelatin according to package directions. Stir until completely dissolved.

Pour a small amount into each sanitized container or petri dish.

Be sure your containers are clean before starting so you are only testing the mold spores collected during the experiment.

Cover the containers with lids, aluminum foil, or plastic wrap while the gelatin cools and solidifies.

The gelatin may develop condensation and moisture as it cools.

Step 2: Swab Different Surfaces

Once the gelatin is fully set, use damp cotton swabs to collect samples from around your house or classroom.

Some fun places to test:

• cell phones
• door handles
• kitchen counters
• stove burners
• refrigerator handles
• bathroom sinks
• TV remotes
• trash can lids
• keyboards
• toys
• hands
• desks

Try testing a variety of different surfaces to compare results.

Step 3: Add the Samples

Label each container using a permanent marker.

Gently rub the q-tip across the surface of the gelatin. Try not to puncture the gelatin surface.

Seal the containers tightly with lids or foil.

Step 4: Place in a Dark Warm Location

Store the containers in a warm location or dark place where mold spores can grow undisturbed.

Within a few days, you may begin to see:

• fuzzy mold colonies
• spots of different colors
• circular growth patterns
• white mycelium strands
• different textures and shapes

We allowed our mold growth experiment to continue for about a week so we could observe lots of mold growth.

Our Results

Before starting the experiment, we made a hypothesis about which surface would grow the most mold.

I was convinced the trash can lid would be the dirtiest surface. Surprisingly, the stove burner ended up growing far more mold than anything else we tested!

My guess is there were tiny food remnants left behind that provided extra nutrients for mold growth.

The kids thought this was both disgusting and fascinating.

Bread Mold Experiment Variation

One of the most popular versions of this activity is the classic bread mold experiment.

To do a bread mold experiment:

1. Place slices of bread into separate sealed bags.
2. Test different variables.
3. Observe mold growth over several days.

Some variables to test:

• touched vs untouched bread
• washed hands vs dirty hands
• refrigerated bread vs room temperature
• moist bread vs dry bread
• bread with preservatives vs homemade bread
• bread stored in a dark place vs sunlight

This is a fantastic mold experiment for science fairs because kids can easily compare results and record observations.

Mold Experiment Variables to Test

Want to extend this activity? Try changing one variable at a time.

Different Foods

Test:

• bread
• apples
• lemons
• cheese
• potatoes
• tortillas

Moisture Levels

Compare:

• dry samples
• damp samples
• soaked samples

Temperature

Test:

• refrigerators
• warm locations
• near a stove
• outdoors

Preservatives

Compare:

• homemade bread
• store-bought bread
• foods with preservatives
• organic foods

Different Surfaces

Swab:

• phones
• keyboards
• bathroom counters
• toys
• shoes
• backpacks

Why Does Mold Grow?

Mold grows best when it has:

• moisture
• warmth
• nutrients
• organic materials

Mold spores land on surfaces constantly, but they only begin growing when conditions are right.

Foods and damp surfaces provide nutrients and moisture that help fungi thrive.

Scientific Method Questions

This mold experiment is perfect for practicing the scientific method. Check out my Scientific Method Printable Pack.

Kids can:

• make a hypothesis
• identify variables
• record observations
• compare results
• analyze data
• draw conclusions

Some questions to explore:

• Which surface grows the most mold?
• Does moisture affect mold growth?
• Which food molds fastest?
• Does refrigeration slow mold growth?
• Do preservatives reduce mold?
• Does light affect fungal growth?

Turn This Into a Science Fair Project

This activity works beautifully as a mold science fair project.

Students can:

• photograph daily changes with digital cameras
• create observation charts
• graph mold growth
• compare different foods
• measure colony size
• test environmental conditions

You could even create petri dish experiments comparing bacteria and fungi growth on different surfaces.

Mold Safety Tips

IMPORTANT: Mold spores can cause allergic reactions and breathing irritation.

For safety:

• keep containers sealed
• wear gloves
• do not inhale mold spores
• do not open containers once mold begins growing
• dispose of samples carefully
• wash hands thoroughly afterward

Adult supervision is recommended.

Book Recommendation

If you want a fantastic book to pair with this activity, we loved Fungus Is Among Us! by Joy Keller and illustrated by Erica Salcedo.

This fun science book teaches kids:

• about fungi
• different types of mold
• mycologists (scientists who study fungi)
• where fungus grows in nature

It makes a perfect companion to this mold experiment for kids.

What Kids Learn from This Mold Experiment

This activity teaches:

• biology
• microbiology
• fungi science
• scientific observation
• scientific method skills
• hypothesis building
• STEM thinking
• laboratory safety

Best of all, it makes science memorable, hands-on, and just the right amount of gross.

Want some other fun science experiments?   Check out my post on Simple Science Experiments!

If your kids enjoyed this mold experiment, they may also love the Rot Museum experiment!